A considerable number of food products are sold with surface coatings to enhance the value of the product. Examples of such coated food products include, but are not limited to, snack foods, cereal food products, food flavorings, and many other segments in the food chain. Many of these products are produced by coating a food substrate such as a cereal product with sweeteners, flavorings or other additives that enhance the product.
Typically, the material to be coated is first immersed or dispersed in a liquid to achieve coating, thus creating difficult solids recovery problems and generating large waste streams. In addition, the coated product usually has a higher moisture level than the uncoated product. Thus, the coated particle must be separated from the liquid and subsequently dried in order to recover the particles.
An apparatus and process for coating small solid particles, such as powdery or granular materials, are described in WO 97/07879 published Mar. 6, 1997 and assigned to E. I. du Pont de Nemours and Company. This process involves metering a liquid composition comprising a coating material, where the liquid composition is either a solution, slurry or melt, into a flow restrictor and injecting a gas stream through the flow restrictor concurrently with the metering of the liquid composition to create a zone of turbulence at the outlet of the flow restrictor, thereby atomizing the liquid composition. The gas stream is heated prior to injecting it through the flow restrictor. A solid particle is added to the zone of turbulence concurrently with the metering of the liquid composition and the injection of the heated gas to mix the solid particle with the atomized liquid composition. The mixing at the zone of turbulence coats the solid particle with the coating material.
WO 97/07676 to E. I. du Pont de Nemours and Company discloses the apparatus of WO 97/07879, along with the use of the apparatus in a process for coating crop protection solid particles. Coatings are water-insoluble, and coating thicknesses are represented by percent rather than thickness.
U.S. Pat. No. 6,015,773, issued to Wysong et al. on Jan. 18, 2000, describes a crop protection composition comprising a mononucleate crop protection solid particle coated with water-insoluble coating material having a diameter in the range from 0.5 to 50 micrometers. This composition is made by a process which results in substantial non-agglomeration of the coated particles.